The spine is broken down into four general regions: cervical (neck), thoracic (upper back), lumbar (lower back) and sacral (tail bone). In a natural aligned spine, the thoracic spine has a kyphotic, or gentle convex curve when viewed from the side. A lordotic lumbar spine, when viewed from the side, has a slightly concave curve. The sacrum is the base of the spine. It is a large triangular fusion of five vertebrae wedged between the pelvic bones. The connection of these bones is called the sacroiliac joint. Back problems can occur where the lumbar spine connects to the sacrum.
Sitting up straight can be difficult for the users of many chairs. In particular, in many seating devices a void exists between the backrest of the chair and the sacrum of a user. As a result, the user of the chair may take a slouched position. By slouching, the user will be placed in a position of poor posture, lack of muscle control and discomfort. Slouching can lead to a number of immediate problems. For example, increased fatigue or fidgeting may result because of discomfort. In addition, undesirable physical effects such as increased pressure on the lumbar discs or the creation of muscle spasms may also result from slouching. Various long-term problems may also occur. For example, pain in the lower back muscles or discomfort between the shoulder blades may result. Also, the tightening of neck muscles and muscle soreness and headaches may result.
In order to avoid problems associated with slouching, previous attempts have been made to provide better support for the sacrum. However, these attempts have generally failed to provide a specific sacral support and contoured fit that will properly position the sacrum, the pelvis, and the supporting neural, muscular, and skeletal systems to provide total pelvic stability. In the past, the void that existed between the sacrum and the back of a work chair failed to provide the preferred support for the sacrum and adjoining tissue.
Somewhat recently, it has been recognized that a spinal support device for applying a directed and concentrated force on the sacrum to properly position the pelvis and spine of a user could be constructed. In U.S. Pat. No. 6,125,851 (Walker), a spinal support device is disclosed that helps support the sacrum of a user to allow the spine to take the preferable shape found in a normal standing posture. While addressing the support of the sacrum, there exists a need to implement proper sacral support in an ergonomic work chair that otherwise properly and comfortably positions a worker for performing tasks.